Experimental and quantum chemical study of the oxidation mechanism of CF2CFBr by O2

M. P. BADENES; J. CZARNOWSKI; C. J. COBOS

Zeitschrift für Physikalische Chemie

Oldenbourg Wissenschaftsverlag

Lugar: München; Año: 2008

0942-9352

The oxidation mechanism of bromotrifluoroethylene, CF2CFBr, by molecular oxygen has been investigated in the gas phase at 416 and 460 K. Based on the CF2CFBr consumption, the yields of the principal product CF2BrC(O)F were 77% and 70% at 416 and 460 K, respectively. Smaller amounts of CF2O, CFBrO and only traces of CF3C(O)F and CO2 were also formed. In the absence of O2, no consumption of CF2CFBr was observed. The oxidation follows a chain mechanism propagated by Br atoms. The energetics of the relevant reaction pathways was studied using different density functional theory methods including more accurate high-level G3 ab initio calculations. The studies revealed that the oxidation is initiated by attack on the carbon atom of the CF2 group of CF2CFBr by the O2. The predicted activation energy for this process is 26.6 kcal mol-1. All other electronic energy barriers and reaction intermediates are below the reagents energy. The theoretical calculations support the proposed reaction mechanism based on previous experimental studies.